In recent years, there has been a massive influx of unaccompanied minors (UMs) crossing the southern border. Under the Trump administration, migrant children are being held in detention centers at ...unprecedented levels, with a fivefold increase in the last year alone. Without legal representation, UMs have little to no capability to defend against removal charges and to advocate for any existing statutory rights that they might have to remain in the United States. UMs need legal advocates to safeguard their constitutional and statutory rights. The need for counsel is arguably greater now than ever as the Trump administration experiments with the hostile immigration practice-characterized as immoral by many religious leaders and inhumane by a bipartisan group of former US attorneys'-of separating children from families at the border. The administration has classified children separated from their families under this policy as UMs. While the administration has since terminated this policy, largely due to nearly uniform global public outrage, hundreds of UMs remain separated from their families, even after a reunification deadline imposed under a federal court order. Unfortunately, the Trump administration has routinely disregarded the humanity of arriving young migrants, subverting the concept of due process in favor of mass detention and deportation.
We present a study of close white dwarf and M dwarf (WD+dM) binary systems and examine the effect that a close companion has on the magnetic field generation in M dwarfs. We use a base sample of 1602 ...white dwarf main-sequence binaries from Rebassa-Mansergas et al. to develop a set of color cuts in GALEX, SDSS, UKIDSS, and 2MASS color space. Then using the SDSS Data Release 8 spectroscopic database, we construct a sample of 1756 WD+dM high-quality pairs from our color cuts and previous catalogs. Using the absolute height above the Galactic plane as a proxy for age, and the H alpha emission line as an indicator for magnetic activity, we investigate the age-activity relation for our sample for spectral types < or =, slant M7. Our results show that early-type M dwarfs (< or =, slantM4) in close binary systems are more likely to be active and have longer activity lifetimes compared to their field counterparts.
We present a catalog of 9316 spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey Data Release 4. We have selected the stars through photometric cuts and spectroscopic modeling, ...backed up by a set of visual inspections. About 6000 of the stars are new discoveries, roughly doubling the number of spectroscopically confirmed white dwarfs. We analyze the stars by performing temperature and surface gravity fits to grids of pure hydrogen and helium atmospheres. Among the rare outliers are a set of presumed helium-core DA white dwarfs with estimated masses below 0.3 M sub( ), including two candidates that may be the lowest-mass yet found. We also present a list of 928 hot subdwarfs.
This paper continues the series presenting cataclysmic variables identified during the fourth year (2003) of the Sloan Digital Sky Survey. We describe 44 close binary systems, of which 12 are the ...previously known systems EN Cet, EG Cnc, V844 Her, GG Leo, Leo 7, CY UMa, DV UMa, EK UMa, EV UMa, UMa 8, EUVE J0854+390, and RX J0859.1+0537 and 32 are new cataclysmic variables. As in the previous papers, the positions, colors, and spectra of all 44 systems are shown, along with follow-up spectroscopic, photometric, and/or polarimetric observations of 15 of the new systems. The new objects include one eclipsing system, eight with prominent He II emission (of which two are confirmed new polars), and 12 systems showing features of the underlying stars. Our spectropolarimetry also confirms EUVE J0854+390 as a polar.
The 28 cataclysmic variables (CVs) found in 2005 in the Sloan Digital Sky Survey are presented with their coordinates, magnitudes, and spectra. Five of these systems are previously known CVs (HH Cnc, ...SX LMi, QZ Ser, AP CrB, and HS 1016+3412), and the rest are new discoveries. Additional spectroscopic, photometric, and/or polarimetric observations of 10 systems were carried out, resulting in estimates of the orbital periods for seven of the new binaries. The 23 new CVs include one eclipsing system, one new Polar, and five systems whose spectra clearly reveal atmospheric absorption lines from the underlying white dwarf.
We present a spectroscopic study and dynamical analysis of ~2600 M7 dwarfs. We confirm our previous finding that the fraction of magnetically active stars decreases with vertical distance from the ...Galactic plane. We also show that the mean luminosity of the Ha emission has a small but statistically significant decrease with distance. Using space motions for ~1300 stars and a simple one-dimensional dynamical simulation, we demonstrate that the drop in the activity fraction of M7 dwarfs can be explained by thin disk dynamical heating and a rapid decrease of magnetic activity at a mean stellar age of ~6-7 Gyr.
We present a new sample of K-band spectral observations for cataclysmic variables (CVs): non-magnetic and magnetic as well as present-day and pre-CVs. The purpose of this diverse sample is to address ...the recent claim that the secondary stars in dwarf novae are carbon deficient, having become so through a far more evolved evolution than the current paradigm predicts. Our new observations, along with previous literature results, span a wide range of orbital period and CV type. In general, dwarf novae in which the secondary star is seen show weak to no CO absorption while polar and pre-CV donor stars appear to have normal CO absorption for their spectral type. However, this is not universal. The presence of normal looking CO absorption in the dwarf nova SS Aur and the hibernating CV QS Vir and a complete lack of CO absorption in the long-period polar V1309 Ori cloud the issue. A summary of the literature pointing to non-solar abundances including enhanced N V/C IV ratios is presented. It appears that some CVs have non-solar abundance material accreting onto the white dwarf suggesting an evolved secondary star while for others CO emission in the accretion disk may play a role. However, the exact mechanism or combination of factors causing the CO absorption anomaly in CVs is not yet clear.
We report Galaxy Evolution Explorer NUV and optical follow-up observations of the cataclysmic variable V455 And at 3 years past its large amplitude dwarf nova outburst. Orbital and superhump ...variations are evident in the NUV and optical light curves. We clearly detect the spin along with a photometric variation that we tentatively attribute to non-radial pulsations in the Discrete Fourier Transforms at both wavelengths. The increased amplitude of the spin and pulsation in the NUV versus the optical implies an origin near the white dwarf. The shorter pulsation period after outburst is indicative of a white dwarf that remains hotter than at quiescence.
The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of the entire sky. Combining the RASS Bright and Faint Source Catalogs yields an average of about three X-ray sources per square ...degree. However, while X-ray source counterparts are known to range from distant quasars to nearby M dwarfs, the RASS data alone are often insufficient to determine the nature of an X-ray source. As a result, large-scale follow-up programs are required to construct samples of known X-ray emitters. We use optical data produced by the Sloan Digital Sky Survey (SDSS) to identify 709 stellar X-ray emitters cataloged in the RASS and falling within the SDSS Data Release 1 footprint. Most of these are bright stars with coronal X-ray emission unsuitable for SDSS spectroscopy, which is designed for fainter objects (g > 15 mag). Instead, we use SDSS photometry, correlations with the Two Micron All Sky Survey and other catalogs, and spectroscopy from the Apache Point Observatory 3.5 m telescope to identify these stellar X-ray counterparts. Our sample of 707 X-ray-emitting F, G, K, and M stars is one of the largest X-ray-selected samples of such stars. We derive distances to these stars using photometric parallax relations appropriate for dwarfs on the main sequence, and use these distances to calculate LX . We also identify a previously unknown cataclysmic variable (CV) as a RASS counterpart. Separately, we use correlations of the RASS and the SDSS spectroscopic catalogs of CVs and white dwarfs (WDs) to study the properties of these rarer X-ray-emitting stars. We examine the relationship between (fX /fg ) and the equivalent width of the Hb emission line for 46 X-ray-emitting CVs and discuss tentative classifications for a subset based on these quantities. We identify 17 new X-ray-emitting DA (hydrogen) WDs, of which three are newly identified WDs. We report on follow-up observations of three candidate cool X-ray-emitting WDs (one DA and two DB (helium) WDs); we have not confirmed X-ray emission from these WDs.
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